The present disclosure generally relates to methods of removing aromatics such as benzene from hydrocarbon streams, and more particularly to membrane, extraction, and hydrogenation methods for removing at least benzene from hydrocarbon streams.
Another aspect of the present disclosure relates to methods of increasing recovery of high purity aromatic benzene, toluene, and xylene (BTX) from hydrocarbon streams, and more particularly to membrane, and extraction methods for enhanced BTX production from hydrocarbon streams.
The Environmental Protection Agency (EPA) has mandated a near complete elimination of benzene from gasoline. More specifically, the benzene limit is set at a maximum of 1.0 volume percent of gasoline. However, if a company elects to use the “yearly pool average” standard of measuring benzene in gasoline, the company's total gasoline pool must meet a yearly benzene average limit of 0.95 volume percent with no gasoline batch exceeding 1.5 volume percent benzene.
For most refiners, the catalytic reformer represents the major source of benzene in the gasoline pool. In catalytic reforming, a hydrocarbon feed such as naphtha is passed over a metal catalyst such as platinum at an elevated temperature and pressure. The catalyst reforms the molecular structure of the hydrocarbons contained in the naphtha by removing hydrogen and rearranging the structure of the molecules so as to improve the octane number of the naphtha. Because of the multiplicity of compounds in the raw naphtha, the actual reactions that take place in the catalytic reformer are numerous.
One strategy to manage benzene production is to minimize benzene and benzene precursors in the reformer feed. While successful in reducing benzene production, benzene is still produced in the reformer. As such, other strategies to manage benzene have been considered where benzene is converted, destroyed, or separated after it is produced in the reformer.
With regard to benzene separation, benzene may be recovered as part of a benzene, toluene, and xylene (BTX) production process, which generally employs staged distillation and extraction. However, distillation is an energy intensive and costly process.
Accordingly, a continual need exists for improved methods of recovering at least benzene from hydrocarbon streams.